FAST VELOCITY ANALYSIS BY FAST VELOCITY ANALYSIS BY PRESTACK WAVEPATH PRESTACK WAVEPATH

MIGRATIONMIGRATION

H. SunH. Sun

Geology and Geophysics Department Geology and Geophysics Department University of UtahUniversity of Utah

WMWM

ModelModel

KM KM

SubSubWMWM

SEG 3-D Salt DataSEG 3-D Salt Data

Horizontal Slice (Depth=1.4 km)Horizontal Slice (Depth=1.4 km)

CPU:CPU:1/170 1/170

CPU:CPU:1/33 1/33

CPU:CPU:1 1

KM KM ((CPU=1CPU=1))

3-D West Texas Data3-D West Texas Data

Sub WM Sub WM ((CPU=1/50CPU=1/50))WM WM ((CPU=1/14CPU=1/14))

Inline Slice (Inline Slice (Offset: 0.4~4.5 kmOffset: 0.4~4.5 km))

0.80.8

3.83.8

Dep

th (

km)

Dep

th (

km)

2-D KM of a Single Event2-D KM of a Single Event

RR SS

AA

AA

2-D WM of a Single Event2-D WM of a Single Event

RR SS

AA

AA

OutlineOutline

• ObjectivesObjectives• Migration Velocity Analysis Migration Velocity Analysis • 2-D Synthetic Data2-D Synthetic Data• 2-D Marine Field Data2-D Marine Field Data• ConclusionsConclusions

ObjectivesObjectives

• Can WMVA effectively improve theCan WMVA effectively improve the migration velocity?migration velocity?

• Whether the WMVA updated velocity Whether the WMVA updated velocity differs much from the KMVA updateddiffers much from the KMVA updated velocity?velocity?

• Can WMVA be much faster than Can WMVA be much faster than KMVA?KMVA?

OutlineOutline

• ObjectivesObjectives• Migration Velocity Analysis Migration Velocity Analysis • 2-D Synthetic Data2-D Synthetic Data• 2-D Marine Field Data2-D Marine Field Data• ConclusionsConclusions

COG MigrationCOG Migration

Pick Layer BoundariesPick Layer Boundaries

Pick Depth Residuals in CIGsPick Depth Residuals in CIGs

Stacked Image & CIGsStacked Image & CIGs

Depth Residual --> Time ResidualDepth Residual --> Time Residual

Ray TracingRay Tracing

Updating: s=s+dsUpdating: s=s+ds

Initial VelocityInitial Velocity

MVAMVAFlow Flow ChartChart

Nemeth1995

OutlineOutline

• ObjectivesObjectives• Migration Velocity Analysis Migration Velocity Analysis • 2-D Synthetic Data2-D Synthetic Data• 2-D Marine Field Data2-D Marine Field Data• ConclusionsConclusions

Correct VelocityCorrect Velocity

00

4040

Dep

th (

m)

Dep

th (

m)

00 5050Offset (m)Offset (m)00 5050Distance (m)Distance (m)

CIGCIGKM ImageKM Image

00

4040

Dep

th (

m)

Dep

th (

m)

1st Iteration1st Iteration 7th Iteration7th IterationKMVAKMVA(1st Layer)(1st Layer)

KMKM KMKM

CIGCIG CIGCIG

VV VV

1st Iteration1st Iteration 7th Iteration7th IterationKMVAKMVA(4th Layer)(4th Layer)

KMKM KMKM

CIGCIG CIGCIG

VV VV

1st Iteration1st Iteration 7th Iteration7th IterationWMVAWMVA(1st Layer)(1st Layer)

WMWM WMWM

CIGCIG CIGCIG

VV VV

1st Iteration1st Iteration 6th Iteration6th IterationWMVAWMVA(4th Layer)(4th Layer)

WMWM WMWM

CIGCIG CIGCIG

VV VV

Correct VelocityCorrect Velocity

00

4040

Dep

th (

m)

Dep

th (

m)

00 505000 5050Distance (m)Distance (m)

WMVA (WMVA (CPU=1CPU=1))KMVA (KMVA (CPU=2CPU=2))

00

4040

Dep

th (

m)

Dep

th (

m)

Distance (m)Distance (m)

OutlineOutline

• ObjectivesObjectives• Migration Velocity Analysis Migration Velocity Analysis • 2-D Synthetic Data2-D Synthetic Data• 2-D Marine Field Data2-D Marine Field Data• ConclusionsConclusions

Initial Migration VelocityInitial Migration Velocity

0000

1818

1.51.5

Horizontal Distance (km)Horizontal Distance (km)

De

pth

(k

m)

De

pth

(k

m) 2.12.1

1.51.5

(k

m /s

)(k

m /s

)

KM Image with Initial VelocityKM Image with Initial Velocity

0000

1818

1.51.5

Horizontal Distance (km)Horizontal Distance (km)

Dep

th (

km)

Dep

th (

km)

BB

TT

KMVA CIGs with Initial VelocityKMVA CIGs with Initial Velocity

00

1.51.5

De

pth

(k

m)

De

pth

(k

m)

1.21.2

KM Image with Initial VelocityKM Image with Initial Velocity0000

18 km18 km

1.51.5

Dep

th (

km)

Dep

th (

km)

00

1.51.5

Dep

th (

km)

Dep

th (

km)

KMVA Velocity Changes in the 1st IterationKMVA Velocity Changes in the 1st Iteration

5050

00

(m

/s)

(m /

s)

KM Image with KM Image with InitialInitial Velocity Velocity0000

18 km18 km

1.51.5

Dep

th (

km)

Dep

th (

km)

00

1.51.5

Dep

th (

km)

Dep

th (

km)

KM Image with KM Image with UpdatedUpdated Velocity Velocity

KM Image with KM Image with InitialInitial Velocity Velocity

KM Image with KM Image with UpdatedUpdated Velocity Velocity

9 km9 km

12601260

Dep

th (

m)

Dep

th (

m)

2 km2 km

10701070

12601260

Dep

th (

m)

Dep

th (

m)

10701070

KMVA CIGs with KMVA CIGs with InitialInitial Velocity Velocity

00

1.51.5

De

pth

(k

m)

De

pth

(k

m)

KMVA CIGs with KMVA CIGs with UpdatedUpdated Velocity Velocity

KMKM Image with Image with InitialInitial Velocity Velocity0000

18 km18 km

1.51.5

Dep

th (

km)

Dep

th (

km)

00

1.51.5

Dep

th (

km)

Dep

th (

km)

WMWM Image with Image with InitialInitial Velocity Velocity

BB

TT

BB

TT

WMVA CIGs with Initial VelocityWMVA CIGs with Initial Velocity

00

1.51.5

De

pth

(k

m)

De

pth

(k

m)

1.21.2

0000

18 km18 km

1.51.5

Dep

th (

km)

Dep

th (

km)

00

1.51.5

Dep

th (

km)

Dep

th (

km)

KMVAKMVA Velocity Changes in the 1st Iteration ( Velocity Changes in the 1st Iteration (CPU=6CPU=6))

5050

00

(m

/s)

(m /

s)

WMVAWMVA Velocity Changes in the 1st Iteration ( Velocity Changes in the 1st Iteration (CPU=1CPU=1))

5050

00

(m

/s)

(m /

s)

0000

18 km18 km

1.51.5

Dep

th (

km)

Dep

th (

km)

00

1.51.5

Dep

th (

km)

Dep

th (

km)

WM Image with WM Image with InitialInitial Velocity Velocity

WM Image with WM Image with UpdatedUpdated Velocity Velocity

WM Image with WM Image with InitialInitial Velocity Velocity

WM Image with WM Image with UpdatedUpdated Velocity Velocity

9 km9 km

12601260

Dep

th (

m)

Dep

th (

m)

2 km2 km

10701070

12601260

Dep

th (

m)

Dep

th (

m)

10701070

WMVA CIGs with WMVA CIGs with InitialInitial Velocity Velocity

00

1.51.5

De

pth

(k

m)

De

pth

(k

m)

WMVA CIGs with WMVA CIGs with UpdatedUpdated Velocity Velocity

0000

18 km18 km

1.51.5

Dep

th (

km)

Dep

th (

km)

00

1.51.5

Dep

th (

km)

Dep

th (

km)

KM Image with KM Image with KMVAKMVA Updated Velocity Updated Velocity

KM Image with KM Image with WMVAWMVA Updated Velocity Updated Velocity

KM Image with KM Image with InitialInitial Velocity Velocity 9 km9 km

12601260

Dep

th (

m)

Dep

th (

m)

2 km2 km

10701070

KM Image with KM Image with KMVAKMVA UpdatedUpdated Velocity Velocity

12601260

Dep

th (

m)

Dep

th (

m)

10701070

KM Image with KM Image with WMVAWMVA UpdatedUpdated Velocity Velocity

12601260

Dep

th (

m)

Dep

th (

m)

10701070

OutlineOutline

• ObjectivesObjectives• Migration Velocity Analysis Migration Velocity Analysis • 2-D Synthetic Data2-D Synthetic Data• 2-D Marine Field Data2-D Marine Field Data• ConclusionsConclusions

• Can WMVA effectively improve theCan WMVA effectively improve the

migration velocity? migration velocity? YesYes

• Whether the WMVA updated velocity Whether the WMVA updated velocity differs much from the KMVA updateddiffers much from the KMVA updated

velocity? velocity? NoNo

ConclusionsConclusions

• Can WMVA be much faster than Can WMVA be much faster than

KMVA? KMVA? YesYes Synthetic data: Synthetic data: twicetwice as fast as KMVA as fast as KMVA Field data : Field data : 6 times6 times faster than KMVA faster than KMVA

• How about 3-D data?How about 3-D data? CouldCould be more than be more than 10 times10 times faster faster

ConclusionsConclusions

AcknowledgementsAcknowledgements

I thank UTAM sponsorsI thank UTAM sponsorsfor their financial supportfor their financial support